Ceramic electronic component

ABSTRACT

A ceramic electronic component that includes an electronic component body having a superficial base ceramic layer; a surface electrode on a surface of the electronic component body; and a covering ceramic layer covering a peripheral section of the surface electrode. The peripheral section of the surface electrode that is covered by the covering ceramic layer has a thin portion located on a central side of the surface electrode and which is thinner than a central section of the surface electrode, and a width of the thin portion is 20% or more of a width of the peripheral section of the surface electrode that is covered by the covering ceramic layer.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of application Ser. No.16/174,623, filed Oct. 30, 2018, which is a continuation ofInternational application No. PCT/JP2017/016377, filed Apr. 25, 2017,which claims priority to Japanese Patent Application No. 2016-098041,filed May 16, 2016, the entire contents of each of which areincorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a ceramic electronic component.

BACKGROUND OF THE INVENTION

For example, a multilayer ceramic electronic component such as amultilayer ceramic substrate is cited as a ceramic electronic componentincluding an electronic component body and a surface electrode placed ona surface thereof.

In such a ceramic electronic component, in order to prevent thedeterioration of high-frequency characteristics of a surface electrode,a covering ceramic layer, i.e., a framing layer, is placed on aperipheral section of the surface electrode (refer to Patent Document1).

-   Patent Document 1: Japanese Unexamined Patent Application    Publication No. 2012-186269

SUMMARY OF THE INVENTION

This covering ceramic layer is placed on a ceramic layer (hereinafterreferred to as the base ceramic layer) of an electronic component bodyin addition to the peripheral section of the surface electrode.

Usually, the covering ceramic layer is formed in such a manner that aceramic green sheet for forming the covering ceramic layer is put on apredetermined place and is fired or ceramic paste for forming thecovering ceramic layer is applied to a predetermined place and is fired.The covering ceramic layer is preferably formed by firing together withfiring for obtaining the electronic component body and the surfaceelectrode.

However, there has been a problem in that a difference in strength iscaused in a covering ceramic layer obtained after firing because thesinterability of a ceramic green sheet or a ceramic paste is differentbetween on a surface electrode and on a base ceramic layer. Inparticular, the strength of the covering ceramic layer on the surfaceelectrode is lower than the strength of the covering ceramic layer onthe base ceramic layer. As a result, there has been a problem in thatthe covering ceramic layer is peeled from the surface electrode in thecase where the ceramic electronic component is subjected to a surfacetreatment such as blasting.

The present invention has been made to solve the above problems. It isan object of the present invention to provide a ceramic electroniccomponent in which the bond strength between a covering ceramic layerand a surface electrode is high and in which the covering ceramic layercan be prevented from being peeled from the surface electrode.

In the case where a covering ceramic layer is obtained by firingtogether with firing for obtaining an electronic component body and asurface electrode, it is conceivable that, during firing, a ceramiccomponent or glass component contained in a base ceramic layertransforms into a liquid phase, which is supplied to the coveringceramic layer, and as a result, the sinterability of the coveringceramic layer is increased. The inventor has conceived that thedifference in amount of the liquid phase supplied to the coveringceramic layer from the base ceramic layer causes the difference insinterability of the covering ceramic layer between on the surfaceelectrode and on the base ceramic layer. That is, the inventor hasconceived that the covering ceramic layer on the surface electrode isunlikely to be supplied with the liquid phase and therefore has poorersinterability as compared to the covering ceramic layer on the baseceramic layer and the bond strength between the covering ceramic layerand the surface electrode is low.

As a consequence, the inventor has found that a covering ceramic layercan be prevented from being peeled from a surface electrode in such amanner that a path for supplying a liquid phase from a base ceramiclayer to the covering ceramic layer on the surface electrode is formedin the surface electrode, thereby completing the present invention.

A ceramic electronic component according to a first embodiment of thepresent invention includes an electronic component body including asuperficial base ceramic layer, a surface electrode placed on a surfaceof the electronic component body, and a covering ceramic layer coveringa peripheral section of the surface electrode. The peripheral section ofthe surface electrode that is covered by the covering ceramic layer hasan opening therein.

In the first embodiment of the present invention, forming the opening inthe peripheral section of the surface electrode that is covered by thecovering ceramic layer allows a liquid phase to be supplied to thecovering ceramic layer from the base ceramic layer through the opening.As a result, the sinterability of the covering ceramic layer on thesurface electrode is increased and the bond strength between thecovering ceramic layer and the surface electrode is increased.Therefore, even in the case where the ceramic electronic component issubjected to a surface treatment such as blasting, the covering ceramiclayer is unlikely to be peeled from the surface electrode.

The liquid phase is supplied to the covering ceramic layer from the baseceramic layer through the opening as described above. Therefore, evenwhen forming a covering ceramic layer having a composition with lowsinterability (for example, a covering ceramic layer in which thecontent of a metal oxide such as Al₂O₃ is high), the bond strengthbetween the covering ceramic layer and the surface electrode is high.

When the bond strength between the covering ceramic layer and thesurface electrode is high, even in the case where a plating layer isformed after the covering ceramic layer is formed, a plating solution isunlikely to penetrate the interface between the surface electrode andthe covering ceramic layer before the plating layer is formed andtherefore the risk of anomalous deposition is low.

Furthermore, forming the opening in the peripheral section of thesurface electrode increases the contact area between the coveringceramic layer and the surface electrode, therefore enhancing ananchoring effect, and increasing the bond strength between the coveringceramic layer and the surface electrode.

In the first embodiment of the present invention, the opening preferablyextends through the surface electrode.

Forming the opening in the peripheral section of the surface electrodesuch that the opening extends through the surface electrode facilitatesthe supply of the liquid phase to the covering ceramic layer on thesurface electrode.

In the first embodiment of the present invention, the opening ispreferably a hole or a slit.

The opening, which is the hole or the slit, can be readily formed by amethod in which screen printing is performed using a screen mask havingan opening, a working method using a laser or a mechanical puncher, orthe like. Therefore, a path for supplying the liquid phase from the baseceramic layer to the covering ceramic layer on the surface electrode canbe readily formed.

A ceramic electronic component according to a second embodiment of thepresent invention includes an electronic component body including asuperficial base ceramic layer, a surface electrode on a surface of theelectronic component body, and a covering ceramic layer covering aperipheral section of the surface electrode. The peripheral section ofthe surface electrode that is covered by the covering ceramic layer hasa thin portion on the peripheral side of the surface electrode and whichis thinner than a central section of the surface electrode. The width ofthe thin portion is 50% or more of the width of the peripheral sectionof the surface electrode that is covered by the covering ceramic layer.

A ceramic electronic component according to a third embodiment of thepresent invention includes an electronic component body including asuperficial base ceramic layer, a surface electrode on a surface of theelectronic component body, and a covering ceramic layer covering aperipheral section of the surface electrode. The peripheral section ofthe surface electrode that is covered by the covering ceramic layer hasa thin portion on the central side of the surface electrode and which isthinner than a central section of the surface electrode. The width ofthe thin portion is 20% or more of the width of the peripheral sectionof the surface electrode that is covered by the covering ceramic layer.

In the second embodiment of the present invention, the thin portion,which is thinner than the central section of the surface electrode,allows a liquid phase to be supplied to the covering ceramic layer fromthe base ceramic layer through the thin portion. As a result, thesinterability of the covering ceramic layer on the surface electrode isincreased and the bond strength between the covering ceramic layer andthe surface electrode is increased. Therefore, even in the case wherethe ceramic electronic component is subjected to a surface treatmentsuch as blasting, the covering ceramic layer is unlikely to be peeledfrom the surface electrode.

In the third embodiment of the present invention, the thin portion,which is thinner than the central section of the surface electrode,allows a liquid phase to be supplied to the covering ceramic layer fromthe base ceramic layer through the thin portion as is the case with thesecond embodiment. In particular, in the third embodiment, the liquidphase is supplied to an end portion of the covering ceramic layer thatis most likely to be peeled off as compared to the second embodiment. Asa result, the sinterability of the covering ceramic layer on the surfaceelectrode is increased and the bond strength between the coveringceramic layer and the surface electrode is increased. Therefore, even inthe case where the ceramic electronic component is subjected to asurface treatment such as blasting, the covering ceramic layer isunlikely to be peeled from the surface electrode.

In each of the second and third embodiments of the present invention,the liquid phase is likely to be supplied to the covering ceramic layerfrom the base ceramic layer through the thin portion as described above.Therefore, even in the case of forming a covering ceramic layer having acomposition with low sinterability (for example, a covering ceramiclayer in which the content of a metal oxide such as Al₂O₃ is high), thebond strength between the covering ceramic layer and the surfaceelectrode is high.

When the bond strength between the covering ceramic layer and thesurface electrode is high, even in the case where a plating layer isformed after the covering ceramic layer is formed, a plating solution isunlikely to penetrate the interface between the surface electrode andthe covering ceramic layer before the plating layer is formed andtherefore the risk of anomalous deposition is low.

In each of the second and third embodiments of the present invention,the width of the thin portion is preferably 15 μm or more and thethickness of the thin portion is preferably 10 μm or less.

Adjusting each of the width and thickness of the thin portion to theabove range facilitates the supply of the liquid phase to the coveringceramic layer on the surface electrode.

The ceramic electronic component according to the first embodiment ofthe present invention, the ceramic electronic component according to thesecond embodiment of the present invention, and the ceramic electroniccomponent according to the third embodiment of the present inventionalso have common shared features.

In the ceramic electronic component according to all embodiments of thepresent invention, the surface electrode preferably includes a firstsintered layer placed on the upper surface of the base ceramic layer, asecond sintered layer placed on the upper surface of the first sinteredlayer, and a plating layer placed on the upper surface of the secondsintered layer.

This allows the surface electrode to have a multilayer structurecomposed of the first sintered layer, which is used to increase the bondstrength to the base ceramic layer, and the second sintered layer, whichis used to form the plating layer. Therefore, the bond strength betweenthe surface electrode and the base ceramic layer can be increased.

In the ceramic electronic component according to all embodiments of thepresent invention, the first sintered layer preferably contains a metaloxide containing at least one metal element selected from Al, Zr, Ti,Si, and Mg.

When the first sintered layer contains the metal oxide, the metal oxidecan be coupled with a ceramic component or glass component contained inthe base ceramic layer. Therefore, the bond strength between the firstsintered layer and the base ceramic layer can be increased.

In the ceramic electronic component according to all embodiments of thepresent invention, the second sintered layer preferably contains asmaller amount of the metal oxide as compared to the first sinteredlayer.

In this case, the upper surface of the second sintered layer can be keptin such a condition that a plating is likely to adhere.

According to all embodiments of the present invention, a ceramicelectronic component in which the bond strength between a coveringceramic layer and a surface electrode is high and the covering ceramiclayer can be prevented from being peeled from the surface electrode canbe provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic sectional view of an example of a ceramicelectronic component according to a first embodiment of the presentinvention.

FIGS. 2A to 2C are schematic sectional views showing an example of amethod for manufacturing the ceramic electronic component 1 shown inFIG. 1 .

FIG. 3 is a schematic sectional view of an example of a ceramicelectronic component according to a second embodiment of the presentinvention.

FIG. 4 is a schematic sectional view of another example of the ceramicelectronic component according to the second embodiment of the presentinvention.

FIG. 5 is a schematic sectional view of another example of the ceramicelectronic component according to the second embodiment of the presentinvention.

FIGS. 6A to 6C are schematic sectional views showing an example of amethod for manufacturing the ceramic electronic component 2 shown inFIG. 3 .

FIG. 7 is a schematic sectional view of an example of a ceramicelectronic component according to a third embodiment of the presentinvention.

FIG. 8 is a schematic plan view showing the shape of openings formed ina peripheral section of a surface electrode in a ceramic electroniccomponent 1-1.

FIG. 9 is a schematic plan view showing the shape of openings formed ina peripheral section of a surface electrode in a ceramic electroniccomponent 1-2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment of a ceramic electronic component according to the presentinvention is described below. However, the present invention is notlimited to the configurations below. Various modifications can be madewithout departing from the spirit of the present invention. Combinationsof two or more of individual preferred configurations of the presentinvention that are described below are included in the scope of thepresent invention.

Embodiments below are illustrative and the partial replacement orcombination of configurations described in different embodiments can bemade. In a second embodiment and subsequent embodiments, items common tothose described in a first embodiment are not described in detail butonly items different from those described therein are described. Inparticular, similar effects due to similar configurations are notmentioned one by one in each embodiment.

In the embodiments below, an embodiment where a ceramic electroniccomponent includes a multilayer ceramic substrate having a plurality oflaminated ceramic layers is described. However, the present invention isnot limited to such a multilayer ceramic electronic component and isapplicable to various ceramic electronic components in which anelectronic component body includes a superficial base ceramic layer andin which a surface electrode is placed on a surface of the electroniccomponent body.

First Embodiment

FIG. 1 is a schematic sectional view of an example of a ceramicelectronic component according to the first embodiment of the presentinvention.

The ceramic electronic component 1, of which the overall configurationis not shown in FIG. 1 , includes an electronic component body 10including a superficial base ceramic layer 11, a surface electrode 20placed on a surface of the electronic component body 10, and a coveringceramic layer 30 covering a peripheral section of the surface electrode20. The peripheral section of the surface electrode 20 that is coveredby the covering ceramic layer 30 has openings 40. The openings 40 arepreferably filled with a ceramic component or glass component, which isnot shown in FIG. 1 , contained in the base ceramic layer 11.

Referring to FIG. 1 , the electronic component body 10 has a multilayerstructure composed of a plurality of laminated base ceramic layers 11and an inner conductive film 12 and via-hole conductor 13 serving asinner wiring conductors are placed in the electronic component body 10.The inner conductive film 12 is electrically connected to the via-holeconductor 13. The via-hole conductor 13 is electrically connected to thesurface electrode 20. The surface electrode 20 has a three-layerstructure and includes a first sintered layer 21 placed on the uppersurface of the base ceramic layer 11 located at a surface of theelectronic component body 10, a second sintered layer 22 placed on theupper surface of the first sintered layer 21, and a plating layer 23placed on the upper surface of the second sintered layer 22.

In this specification, a section of a surface electrode that is coveredby a covering ceramic layer is referred to as a peripheral section ofthe surface electrode and a section of the surface electrode that is notcovered by the covering ceramic layer is referred to as a centralsection of the surface electrode. The peripheral section of the surfaceelectrode that is covered by the covering ceramic layer is hereinaftersimply referred to as the peripheral section of the surface electrode.

Likewise, when the surface electrode has a multilayer structure, asection covered by the covering ceramic layer is referred to as aperipheral section of each layer and a section not covered by thecovering ceramic layer is referred to as a central section of the layer.

As shown in FIG. 1 , in the ceramic electronic component 1, theperipheral section of the surface electrode 20 is covered by thecovering ceramic layer 30, which is placed on the base ceramic layer 11and the second sintered layer 22, and has the openings 40. The openings40 extend through the first sintered layer 21 and the second sinteredlayer 22. On the other hand, a central section of the surface electrode20 is provided with the plating layer 23. The plating layer 23 is notcovered by the covering ceramic layer 30.

The base ceramic layer, which is included in the electronic componentbody, preferably contains a low-temperature co-fired ceramic material.The low-temperature co-fired ceramic material refers to, among ceramicmaterials, a material which can be sintered at a firing temperature of1,000° C. or less and which can be co-fired with Ag or Cu.

Examples of the low-temperature co-fired ceramic material, which iscontained in the base ceramic layer, include glass compositelow-temperature co-fired ceramic materials formed by mixing borosilicateglass with ceramic materials such as quartz, alumina, and forsterite;crystal glass low-temperature co-fired ceramic materials containingZnO—MgO—Al₂O₃—SiO₂ crystal glass; and non-glass low-temperature co-firedceramic materials formed using BaO—Al₂O₃—SiO₂ ceramic materials orAl₂O₃—CaO—SiO₂—MgO—B₂O₃ ceramic materials.

Inner wiring conductors (the inner conductive film and the via-holeconductor), which are placed in the electronic component body, contain aconductive component. Examples of the conductive component, which iscontained in the inner wiring conductors, include Au, Ag, Cu, Pt, Ta, W,Ni, Fe, Cr, Mo, Ti, Pd, Ru, and alloys mainly containing one of thesemetals. The inner wiring conductors preferably contain Au, Ag, or Cu andmore preferably Ag or Cu as a conductive component. Au, Ag, and Cu havelow resistance and are therefore particularly suitable for the casewhere the ceramic electronic component is for use in high-frequencyapplications.

The covering ceramic layer, which covers the peripheral section of thesurface electrode, is placed on the base ceramic layer located at thesurface of the electronic component body and the surface electrode.

The covering ceramic layer preferably contains a low-temperatureco-fired ceramic material. In this case, the low-temperature co-firedceramic material contained in the covering ceramic layer may be the sameas or different from the low-temperature co-fired ceramic materialcontained in the base ceramic layer and is preferably the same as thelow-temperature co-fired ceramic material contained in the base ceramiclayer.

The covering ceramic layer may contain the same metal oxide as a metaloxide which is contained in the first sintered layer of the surfaceelectrode as described below and preferably contains substantially nometal oxide. When the covering ceramic layer contains the metal oxide,the content of the metal oxide in the covering ceramic layer ispreferably less than 50% by weight.

The thickness of the covering ceramic layer is not particularly limitedand is preferably 0.5 μm to 40 μm.

The surface electrode, which is placed on the surface of the electroniccomponent body, is one connected to another electronic component such asa wiring board or a mounted component. The surface electrode isconnected to the other electronic component by soldering or the like.

Examples of a conductive component contained in the surface electrodeinclude Au, Ag, Cu, Pt, Ta, W, Ni, Fe, Cr, Mo, Ti, Pd, Ru, and alloysmainly containing one of these metals. The surface electrode preferablycontains the same conductive component as that contained in the innerwiring conductors. In particular, the surface electrode preferablycontains Au, Ag, or Cu and more preferably Ag or Cu as a conductivecomponent.

The width (the length represented by W1 in FIG. 1 ) of the peripheralsection of the surface electrode is not particularly limited and ispreferably 15 μm to 1 mm.

In this specification, the width of the peripheral section of thesurface electrode refers to the distance from the periphery of thesurface electrode to the inner edge of the covering ceramic layer.

In the first embodiment of the present invention, the peripheral sectionof the surface electrode that is covered by the covering ceramic layercharacteristically has the openings. The openings are preferably filledwith the ceramic component or glass component contained in the baseceramic layer.

The peripheral section of the surface electrode may be provided with asingle opening and is preferably provided with a plurality of openings.

The openings, which are placed in the peripheral section of the surfaceelectrode, may extend through the surface electrode and may be open to aprincipal surface of the surface electrode without extending through thesurface electrode. The openings preferably extend through the surfaceelectrode. When the openings do not extend through the surfaceelectrode, the distance from a principal surface of the surfaceelectrode that has no openings to each opening is preferably 10 μm orless.

When the peripheral section of the surface electrode has a plurality ofthe openings, all of the openings preferably extend through the surfaceelectrode and openings extending through the surface electrode andopenings not extending through the surface electrode may be present in amixed state.

A location where the openings are placed is not particularly limited andis preferably the peripheral section of the surface electrode. Theopenings are preferably uniformly placed in the peripheral section ofthe surface electrode.

The openings, which are placed in the peripheral section of the surfaceelectrode, are preferably holes or slits.

The planar shape of the holes is preferably substantially circular orregularly polygonal and is more preferably substantially circular orsquare. The planar shape of the slits is preferably substantially ovalor rectangular.

When the peripheral section of the surface electrode is provided with ahole or a slit, one or more holes only may be placed, one or more slitsonly may be placed, or holes and slits may be present in a mixed state.When the peripheral section of the surface electrode is provided with aplurality of holes, the holes may have different shapes and preferablyhave the same shape. This applied to slits.

The surface electrode may have a single-layer structure or a multilayerstructure and preferably has the multilayer structure.

When the surface electrode has the single-layer structure, the surfaceelectrode is preferably composed of a sintered layer only.

When the surface electrode has the multilayer structure, the multilayerstructure is preferably an at least two-layer structure including asintered layer placed on the upper surface of the base ceramic layerlocated at the surface of the electronic component body and a platinglayer placed on the upper surface of the sintered layer and is morepreferably an at least three-layer structure including a first sinteredlayer placed on the upper surface of the base ceramic layer located atthe surface of the electronic component body, a second sintered layerplaced on the upper surface of the first sintered layer, and a platinglayer placed on the upper surface of the second sintered layer.

The sintered layers are those formed by baking conductive paste and theplating layers are those formed by electroplating or electroless platingafter the sintered layers are formed.

When the surface electrode has the multilayer structure, the surfaceelectrode preferably includes a plating layer located outermost and thesurface electrode preferably includes a sintered layer only withoutincluding any plating layer. When the surface electrode includes theplating layer located outermost, the plating layer is usually formedafter the sintered layers and the covering ceramic layer are formed.Therefore, the plating layer is not covered by the covering ceramiclayer.

The first sintered layer, second sintered layer, and plating layer ofthe surface electrode are described below. The first sintered layer,which is included in the surface electrode, contains a conductivecomponent. In order to increase the bond strength to the electroniccomponent body, the first sintered layer preferably further contains ametal oxide.

Examples of the conductive component contained in the first sinteredlayer include Au, Ag, Cu, Pt, Ta, W, Ni, Fe, Cr, Mo, Ti, Pd, Ru, andalloys mainly containing one of these metals. The first sintered layerpreferably contains the same conductive component as that contained inthe inner wiring conductors. In particular, the first sintered layerpreferably contains Au, Ag, or Cu and more preferably Ag or Cu as aconductive component.

The metal oxide contained in the first sintered layer is, for example, ametal oxide containing at least one metal element selected from thegroup consisting of Al, Zr, Ti, Si, and Mg. The metal oxide may be usedalone or in combination with one or more metal oxides. Among these, ametal oxide containing at least one metal element selected from thegroup consisting of Al, Zr, and Ti is preferable and a metal oxidecontaining Al element is more preferable.

The content of the metal oxide in the first sintered layer is notparticularly limited and is preferably higher than the content of thecontent of the metal oxide in the second sintered layer. In particular,the content of the metal oxide in the first sintered layer is preferably1% by weight or more and more preferably 3% by weight or more. On theother hand, the content of the metal oxide in the first sintered layeris preferably less than 10% by weight and more preferably less than 5%by weight.

When the first sintered layer contains the metal oxide, particles ofmetal contained in the conductive component and particles of the metaloxide may be present in a dispersed state and surroundings of the metalparticles may be covered by the metal oxide. The surroundings of themetal particles are preferably covered by the metal oxide. When thesurroundings of the metal particles are covered by the metal oxide, thebond strength to the electronic component body can be increased even ifthe content of the metal oxide is low.

The planar shape of the first sintered layer is not particularly limitedand is, for example, rectangular, tetragonal, polygonal rather thantetragonal, circular, or oval.

The second sintered layer, which is included in the surface electrode,contains a conductive component. The conductive component contained inthe second sintered layer is preferably the same as the conductivecomponent contained in the first sintered layer.

The second sintered layer may contain the same metal oxide as the metaloxide contained in the first sintered layer. When the content of themetal oxide therein is high, a plating is unlikely to adhere to theupper surface of the second sintered layer. Therefore, the secondsintered layer preferably contains a smaller amount of the metal oxideas compared to the first sintered layer and more preferably containssubstantially no metal oxide. In the case where the second sinteredlayer contains the metal oxide, the content of the metal oxide in thesecond sintered layer is preferably less than 1% by weight when thecontent of the metal oxide in the first sintered layer is 1% by weightto less than 10% by weight. When the content of the metal oxide in thefirst sintered layer is 3% by weight to less than 5% by weight, thecontent of the metal oxide in the second sintered layer is preferablyless than 3% by weight and more preferably less than 1% by weight.

The area of the upper surface of the second sintered layer is preferablysubstantially the same as the area of the upper surface of the firstsintered layer. That is, the planar shape of the second sintered layeris preferably substantially the same as the planar shape of the firstsintered layer.

The number of sintered layers is not limited to two and another sinteredlayer may be placed between the first sintered layer, which is placed onthe upper surface of the base ceramic layer, and the second sinteredlayer, of which the upper surface is overlaid with the plating layer.

The plating layer, which is included in the surface electrode, ispreferably made of Au, Ag, Ni, Pd, Cu, Sn, or an alloy containing thesemetals. The plating layer, which is included in the surface electrode,may be a plating layer composed of a plurality of sublayers such as anickel plating sublayer and gold plating sublayer that are the firstsublayer and the second sublayer, respectively, from the second sinteredlayer side; a nickel plating sublayer and tin plating sublayer that arethe first sublayer and the second sublayer, respectively, from thesecond sintered layer side; and a nickel plating sublayer, palladiumplating sublayer, and gold plating sublayer that are the first sublayer,the second sublayer, and the third sublayer, respectively, from thesecond sintered layer side.

A section provided with the covering ceramic layer is provided with noplating layer. Therefore, the area of the upper surface of the platinglayer is preferably less than the area of the upper surface of thesecond sintered layer.

The thickness of the plating layer is not particularly limited and ispreferably 1 μm to 10 μm.

The ceramic electronic component 1 shown in FIG. 1 is preferablymanufactured as described below. FIGS. 2A to 2C are schematic sectionalviews showing an example of a method for manufacturing the ceramicelectronic component 1 shown in FIG. 1 .

First, an unsintered multilayer body 100 is prepared as shown in FIG.2A.

In order to prepare the unsintered multilayer body 100, a plurality ofbase ceramic green sheets 111 are prepared. The base ceramic greensheets 111 are those converted into the base ceramic layers 11 afterfiring.

The base ceramic green sheets are those obtained by forming, forexample, slurry containing a powder of a ceramic raw material such as alow-temperature co-fired ceramic material, an organic binder, and asolvent into sheets by a doctor blade process or the like. The slurrymay contain various additives such as a dispersant and a plasticizer.

The organic binder contained in the slurry may be, for example, abutyral resin (polyvinyl butyral), an acrylic resin, a methacrylicresin, or the like. The solvent may be, for example, toluene, an alcoholsuch as isopropyl alcohol, or the like. The plasticizer may be, forexample, di-n-butyl phthalate or the like.

Next, a through-hole for forming the via-hole conductor 13 is formed ina specific one of the base ceramic green sheets 111. The through-hole isfilled with a conductive paste containing, for example, Ag or Cu as aconductive component, whereby a conductive paste body 113 to beconverted into the via-hole conductor 13 is formed.

A conductive paste film 112 to be converted into the inner conductivefilm 12 is formed on a specific one of the base ceramic green sheets 111by, for example, a process such as screen printing using a conductivepaste having the same composition as that of the above conductive paste.

Furthermore, a conductive paste film 121 to be converted into the firstsintered layer 21 is formed on the base ceramic green sheet 111 placedsuperficially after stacking. A conductive paste film 122 to beconverted into the second sintered layer 22 is formed on the conductivepaste film 121. The conductive paste film 121 to be converted into thefirst sintered layer 21 can be formed by a process such as screenprinting using, for example, a conductive paste containing a conductivecomponent such as Ag or Cu and a metal oxide such as Al₂O₃. Theconductive paste film 122 to be converted into the second sintered layer22 can be formed by a process such as screen printing using, forexample, a conductive paste containing a conductive component such as Agor Cu. In this operation, the conductive paste film 121 and theconductive paste film 122 are formed so as to have openings such thatopenings 140 are formed so as to extend through the conductive pastefilm 121 to be converted into the first sintered layer 21 and theconductive paste film 122 to be converted into the second sintered layer22. Alternatively, after the conductive paste film 121 and theconductive paste film 122 are formed, the openings are formed therein.After the base ceramic green sheets 111 are stacked, the conductivepaste film 121 to be converted into the first sintered layer 21 and theconductive paste film 122 to be converted into the second sintered layer22 may be formed before firing. Examples of the metal oxide contained inthe conductive paste include Al₂O₃, ZrO₂, TiO₂, SiO₂, and MgO. Amongthese oxides, Al₂O₃ is preferably used.

Examples of a method for forming the conductive paste films having theopenings include a method in which screen printing is performed using ascreen mask having openings and a method in which after a conductivepaste film is formed on a transfer film such as a PET film and openingsare formed in the conductive paste film on the transfer film using amechanical puncher, the conductive paste film is transferred to a baseceramic green sheet. An example of a method for forming the openingsafter the formation of the conductive paste films is a method in whichafter a conductive paste film is formed on a base ceramic green sheet,openings are formed in the conductive paste film only using a laser orthe like.

A covering ceramic green sheet 130 is separately prepared. The coveringceramic green sheet 130 is one converted into the covering ceramic layer30 after firing.

The covering ceramic green sheet is one obtained by forming, forexample, slurry containing a powder of a ceramic raw material such as alow-temperature co-fired ceramic material, an organic binder, and asolvent into a sheet by a doctor blade process or the like. The slurrymay contain various additives such as a dispersant and a plasticizer.The slurry for preparing the covering ceramic green sheet may be theslurry for preparing the base ceramic green sheets.

Subsequently, the unsintered multilayer body 100 is prepared by stackingand then pressure-bonding the base ceramic green sheet 111 provided withthe conductive paste body 113 to be converted into the via-holeconductor 13 or the conductive paste film 112 to be converted into theinner conductive film 12, the base ceramic green sheets 111 providedwith the conductive paste film 121 to be converted into the firstsintered layer 21 and the conductive paste film 122 to be converted intothe second sintered layer 22, and the covering ceramic green sheet 130.The covering ceramic green sheet 130 is provided on the base ceramicgreen sheet 111 placed superficially after stacking and the conductivepaste film 122 to be converted into the second sintered layer 22 so asto cover a region provided with the openings 140.

The unsintered multilayer body 100 can be prepared in such a mannerthat, instead of the covering ceramic green sheet 130, a paste-likecomposition is applied to the base ceramic green sheet 111 located at asurface of the unsintered multilayer body 100 and the conductive pastefilm 122 to be converted into the second sintered layer 22. In thiscase, the paste-like composition may be applied to the unstacked baseceramic green sheet 111 and the conductive paste film 122 to beconverted into the second sintered layer 22.

Thereafter, the unsintered multilayer body 100 is fired. This allows thefollowing body to be obtained as shown in FIG. 2B: a multilayer bodyincluding the electronic component body 10, which includes the baseceramic layer 11 placed superficially; the first sintered layer 21,which is placed on the upper surface of the base ceramic layer 11; thesecond sintered layer 22, which is placed on the upper surface of thefirst sintered layer 21; and the covering ceramic layer 30, which isplaced on the base ceramic layer 11 and the second sintered layer 22.Peripheral sections of the first and second sintered layers 21 and 22that are covered by the covering ceramic layer 30 are provided with theopenings 40. The ceramic component or the glass component, which iscontained in the base ceramic layer 11, transforms into a liquid phase,which is not shown in FIG. 2B, during firing. The liquid phase issupplied to the covering ceramic layer 30 (the covering ceramic greensheet 130) from the base ceramic layer 11 (the base ceramic green sheets111) through the openings 40. Therefore, the openings 40 are preferablyfilled with the ceramic component or the glass component, which iscontained in the base ceramic layer 11.

The first sintered layer and the second sintered layer can be formed insuch a manner that the conductive paste films are formed on a surface ofthe sintered electronic component body and are fired. The coveringceramic layer can be formed in such a manner that the covering ceramicgreen sheet is provided on the peripheral sections of the first andsecond sintered layers after sintering and is fired. The first sinteredlayer, the second sintered layer, and the covering ceramic layer arepreferably formed in such a manner that the conductive paste films andthe covering ceramic green sheet are fired together with firing forobtaining the electronic component body as described above. Forming thefirst sintered layer, the second sintered layer, and the coveringceramic layer by co-firing is advantageous in streamlining manufacturingsteps and in reducing manufacturing costs and enables the bond strengthbetween the electronic component body and the first sintered layer andthe bond strength between the electronic component body and the coveringceramic layer to be increased. In the case of forming the first sinteredlayer, the second sintered layer, and the covering ceramic layer byco-firing, the base ceramic layer, which is included in the electroniccomponent body, preferably contains the low-temperature co-fired ceramicmaterial as described above.

A constraint green sheet mainly containing a metal oxide (Al₂O₃ or thelike) not substantially sintered at the sintering temperature of theunsintered multilayer body 100 is prepared. The unsintered multilayerbody 100 may be fired in such a state that the constraint green sheet isplaced on a surface of the unsintered multilayer body 100. In this case,the constraint green sheet is not substantially sintered during firing,therefore does not shrink, and acts to suppress the shrinkage of themultilayer body in the principal surface direction.

After the unsintered multilayer body 100 is fired, the plating layer 23is formed on the upper surface of the second sintered layer 22 byelectroplating or electroless plating as shown in FIG. 2C. For theplating layer 23, it is preferable that a Ni plating film is formed onthe second sintered layer 22 and an Au or Sn plating film is formedthereon. The above allows the ceramic electronic component 1, in whichthe surface electrode 20 including the first sintered layer 21, thesecond sintered layer 22, and the plating layer 23 is placed on asurface of the electronic component body 10 and the covering ceramiclayer 30 covers the peripheral section of the surface electrode 20, tobe obtained.

In the first embodiment of the present invention, forming the openingsin the peripheral section of the surface electrode that is covered bythe covering ceramic layer probably allows the liquid phase to besupplied to the covering ceramic layer from the base ceramic layerthrough the openings. As a result, the sinterability of the coveringceramic layer on the surface electrode is increased and the bondstrength between the covering ceramic layer and the surface electrode isincreased. Therefore, even in the case where the ceramic electroniccomponent is subjected to a surface treatment such as blasting, thecovering ceramic layer is unlikely to be peeled from the surfaceelectrode.

Furthermore, forming the openings in the peripheral section of thesurface electrode increases the contact area between the coveringceramic layer and the surface electrode, therefore enhances an anchoringeffect, and increases the bond strength between the covering ceramiclayer and the surface electrode.

Second Embodiment

FIG. 3 is a schematic sectional view of an example of a ceramicelectronic component according to a second embodiment of the presentinvention.

The ceramic electronic component 2, of which the overall configurationis not shown in FIG. 3 , includes an electronic component body 10including a superficial base ceramic layer 11, a surface electrode 20placed on a surface of the electronic component body 10, and a coveringceramic layer 30 covering a peripheral section of the surface electrode20.

The peripheral section of the surface electrode 20 that is covered bythe covering ceramic layer 30 has a thin portion 50 which is present onthe peripheral side of the surface electrode 20 and which is thinnerthan a central section of the surface electrode 20.

Referring to FIG. 3 , the electronic component body 10 has a multilayerstructure composed of a plurality of laminated base ceramic layers 11and an inner conductive film 12 and via-hole conductor 13 serving asinner wiring conductors are placed in the electronic component body 10.The inner conductive film 12 is electrically connected to the via-holeconductor 13. The via-hole conductor 13 is electrically connected to thesurface electrode 20. The surface electrode 20 has a three-layerstructure and includes a first sintered layer 21 placed on the uppersurface of the base ceramic layer 11 located at a surface of theelectronic component body 10, a second sintered layer 22 placed on theupper surface of the first sintered layer 21, and a plating layer 23placed on the upper surface of the second sintered layer 22.

As described above, in this specification, a section of a surfaceelectrode that is covered by a covering ceramic layer is referred to asa peripheral section of the surface electrode and a section of thesurface electrode that is not covered by the covering ceramic layer isreferred to as a central section of the surface electrode.

As shown in FIG. 3 , in the ceramic electronic component 2, theperipheral section of the surface electrode 20 is covered by thecovering ceramic layer 30, which is placed on the base ceramic layer 11and the second sintered layer 22. The whole of the peripheral section ofthe surface electrode 20 corresponds to the thin portion 50, which isthinner than the central section of the surface electrode 20. On theother hand, the central section of the surface electrode 20 is providedwith the plating layer 23. The plating layer 23 is not covered by thecovering ceramic layer 30.

FIG. 4 is a schematic sectional view of another example of the ceramicelectronic component according to the second embodiment of the presentinvention.

In a ceramic electronic component 3 shown in FIG. 4 , a portion of aperipheral section of a surface electrode 20 is a thin portion 50thinner than a central section of the surface electrode 20.

A material for the base ceramic layers, which are included in theelectronic component body; a conductive component in inner wiringconductors placed in the electronic component body; and the like are thesame as those described in the first embodiment.

The covering ceramic layer, which covers the peripheral section of thesurface electrode, is placed on the base ceramic layer located at thesurface of the electronic component body and the surface electrode.

A material contained in the covering ceramic layer, the thickness of thecovering ceramic layer, and the like are the same as those described inthe first embodiment.

The surface electrode, which is placed on a surface of the electroniccomponent body, is one connected to another electronic component such asa wiring board or a mounted component. The surface electrode isconnected to the other electronic component by soldering or the like.

A conductive component contained in the surface electrode is the same asthat described in the first embodiment.

In the second embodiment of the present invention, the peripheralsection of the surface electrode that is covered by the covering ceramiclayer has the thin portion, which is present on the peripheral side ofthe surface electrode and is thinner than the central section of thesurface electrode. In other words, in the second embodiment of thepresent invention, a thin portion having a predetermined width ispresent from the peripheral side to central side of the surfaceelectrode, with the periphery of the surface electrode being an endportion on the peripheral side.

The width (the length represented by W1 in FIGS. 3 and 4 ) of theperipheral section of the surface electrode is not particularly limitedand is preferably 15 μm to 1 mm.

As described above, in this specification the width of the peripheralsection of the surface electrode refers to the distance from theperiphery of the surface electrode to the inner edge of the coveringceramic layer.

The width (the length represented by W2 in FIGS. 3 and 4 ) of the thinportion is preferably 10 μm or more, more preferably 15 μm or more, andfurther more preferably 20 μm or more.

In the second embodiment of the present invention, the width of the thinportion refers to the distance from the periphery of the surfaceelectrode to a portion having the same thickness as the thickness of thecentral section.

The width of the peripheral section of the surface electrode and thewidth of the thin portion can be both measured by cross-sectionalobservation using a scanning electron microscope (SEM).

In the second embodiment of the present invention, the width of the thinportion is preferably 50% or more of the width of the peripheral sectionof the surface electrode that is covered by the covering ceramic layer.That is, it is characteristic that the ratio (W2/W1) of the width W2 ofthe thin portion to the width W1 of the peripheral section of thesurface electrode is 50% or more as shown in FIGS. 3 and 4 . Referringto FIG. 3 , for example, the width W2 of the thin portion is the same asthe width W1 of the peripheral section of the surface electrode andtherefore the width of the thin portion is 100% of the width of theperipheral section of the surface electrode.

The width of the thin portion is preferably 70% or more of the width ofthe peripheral section of the surface electrode that is covered by thecovering ceramic layer, more preferably 90% or more, and particularlypreferably 100%. The case where the ratio of the width of the thinportion is 100% corresponds to a third embodiment of the presentinvention.

The width of the thin portion may exceed 100% of the width of theperipheral section of the surface electrode that is covered by thecovering ceramic layer. In this case, the central section of the surfaceelectrode that is not covered by the covering ceramic layer has the thinportion. The central section of the surface electrode that is notcovered by the covering ceramic layer may have the thin portion asdescribed above. Only the peripheral section of the surface electrodepreferably has the thin portion.

The thin portion preferably has a thickness of 10 μm or less and morepreferably 5 μm or less.

The thickness of the thin portion can be measured by cross-sectionalobservation using a scanning electron microscope (SEM).

The thickness of the thin portion is preferably constant over the wholethin portion as shown in FIGS. 3 and 4 . The thickness of the thinportion may decrease stepwise from the central section of the surfaceelectrode toward the peripheral section thereof or may decreasecontinuously.

In the peripheral section of the surface electrode, the thin portion ispreferably present over the whole of a region including the periphery ofthe surface electrode so as to surround the periphery of the surfaceelectrode and a portion having the same thickness as the thickness ofthe central section may be present in a portion of the region includingthe periphery of the surface electrode. The peripheral section of thesurface electrode may have a plurality of thin portions.

The surface electrode may have a single-layer structure or a multilayerstructure and preferably has the multilayer structure.

When the surface electrode has the single-layer structure, the surfaceelectrode is preferably composed of a sintered layer only.

When the surface electrode has the multilayer structure, the multilayerstructure is preferably an at least two-layer structure including asintered layer placed on the upper surface of the base ceramic layerlocated at the surface of the electronic component body and a platinglayer placed on the upper surface of the sintered layer and is morepreferably an at least three-layer structure including a first sinteredlayer placed on the upper surface of the base ceramic layer located atthe surface of the electronic component body, a second sintered layerplaced on the upper surface of the first sintered layer, and a platinglayer placed on the upper surface of the second sintered layer.

The configurations of sintered layers such as the first sintered layerand the second sintered layer and the plating layer are the same asthose described in the first embodiment and therefore are not describedin detail.

FIG. 5 is a schematic sectional view of another example of the ceramicelectronic component according to the second embodiment of the presentinvention.

In a ceramic electronic component 4 shown in FIG. 5 , a peripheralsection of a first sintered layer 21 has an exposed surface on which nosecond sintered layer 22 or plating layer 23 is placed. The exposedsurface is covered by a covering ceramic layer 30 placed on a baseceramic layer 11 located at a surface of an electronic component body 10and the first sintered layer 21. Thus, the peripheral section of thefirst sintered layer 21 that is covered by the covering ceramic layer 30is a thin portion 50 thinner than a central section of a surfaceelectrode 20.

When the surface electrode has a multilayer structure as describedabove, the number of layers included in the thin portion may bedifferent from the number of layers included in the surface electrode.

The ceramic electronic component 2 shown in FIG. 3 is preferablymanufactured as described below.

FIGS. 6A to 6C are schematic sectional views showing an example of amethod for manufacturing the ceramic electronic component 2 shown inFIG. 3 .

The manufacturing method shown in FIGS. 6A to 6C is the same as themanufacturing method shown in FIGS. 2A to 2C except a method for formingthe surface electrode 20 and therefore common items are not described indetail.

First, an unsintered multilayer body 200 is prepared as shown in FIG.6A.

In order to prepare the unsintered multilayer body 200, a plurality ofbase ceramic green sheets 111 are prepared and, thereafter, a conductivepaste body 113 to be converted into the via-hole conductor 13 or aconductive paste film 112 to be converted into the inner conductive film12 is formed on a specific one of the base ceramic green sheets 111 asis the case with the first embodiment. A covering ceramic green sheet130 is separately prepared.

Furthermore, a conductive paste film 121 to be converted into the firstsintered layer 21 is formed on the base ceramic green sheet 111 placedsuperficially after stacking and a conductive paste film 122 to beconverted into the second sintered layer 22 is formed on the conductivepaste film 121. In this operation, the conductive paste film 121 and theconductive paste film 122 are formed by varying the amount of an appliedconductive paste such that a thin portion 150 in which a peripheralsection is thinner than a central section is formed.

Subsequently, the unsintered multilayer body 200 is prepared by stackingand then pressure-bonding the base ceramic green sheet 111 provided withthe conductive paste body 113 to be converted into the via-holeconductor 13 or the conductive paste film 112 to be converted into theinner conductive film 12, the base ceramic green sheet 111 provided withthe conductive paste film 121 to be converted into the first sinteredlayer 21 and the conductive paste film 122 to be converted into thesecond sintered layer 22, and the covering ceramic green sheet 130. Thecovering ceramic green sheet 130 is provided on the base ceramic greensheet 111 placed superficially after stacking and the conductive pastefilm 122 to be converted into the second sintered layer 22 so as tocover peripheral sections of the conductive paste films 121 and 122 thathave a reduced thickness.

Thereafter, the unsintered multilayer body 200 is fired. This allows thefollowing body to be obtained as shown in FIG. 6B: a multilayer bodyincluding the electronic component body 10, which includes thesuperficial base ceramic layer 11; the first sintered layer 21, which isplaced on the upper surface of the base ceramic layer 11; the secondsintered layer 22, which is placed on the upper surface of the firstsintered layer 21; and the covering ceramic layer 30, which is placed onthe base ceramic layer 11 and the second sintered layer 22. Peripheralsections of the first and second sintered layers 21 and 22 that arecovered by the covering ceramic layer 30 are provided with the thinportion 50.

After the unsintered multilayer body 200 is fired, the plating layer 23is formed on the upper surface of the second sintered layer 22 byelectroplating or electroless plating as shown in FIG. 6C. The aboveallows the ceramic electronic component 2, in which the surfaceelectrode 20 including the first sintered layer 21, the second sinteredlayer 22, and the plating layer 23 is placed on a surface of theelectronic component body 10 and the covering ceramic layer 30 coversthe peripheral section of the surface electrode 20, to be obtained.

In the second embodiment of the present invention, in the peripheralsection of the surface electrode that is covered by the covering ceramiclayer, forming the thin portion, which is thinner than the centralsection of the surface electrode, on the peripheral side of the surfaceelectrode and adjusting the width of the thin portion to 50% or more ofthe width of the peripheral section of the surface electrode probablyallows a liquid phase to be supplied to the covering ceramic layer fromthe base ceramic layer through the thin portion. As a result, thesinterability of the covering ceramic layer on the surface electrode isincreased and the bond strength between the covering ceramic layer andthe surface electrode is increased. Therefore, even in the case wherethe ceramic electronic component is subjected to a surface treatmentsuch as blasting, the covering ceramic layer is unlikely to be peeledfrom the surface electrode.

Third Embodiment

FIG. 7 is a schematic sectional view of an example of a ceramicelectronic component according to the third embodiment of the presentinvention.

The ceramic electronic component 5, of which the overall configurationis not shown in FIG. 7 , includes an electronic component body 10including a superficial base ceramic layer 11, a surface electrode 20placed on a surface of the electronic component body 10, and a coveringceramic layer 30 covering a peripheral section of the surface electrode20.

The peripheral section of the surface electrode 20 that is covered bythe covering ceramic layer 30 has a thin portion 50 which is present onthe central side of the surface electrode 20 and which is thinner than acentral section of the surface electrode 20.

In the third embodiment of the present invention, the peripheral sectionof the surface electrode that is covered by the covering ceramic layerhas the thin portion, which is present on the central side of thesurface electrode and is thinner than the central section of the surfaceelectrode. In other words, in the third embodiment of the presentinvention, a thin portion having a predetermined width is present fromthe central side to peripheral side of the surface electrode. As shownin FIG. 7 , an end of the thin portion that is located on the centralside of the surface electrode preferably coincides with the position ofthe inner edge of the covering ceramic layer.

In the peripheral section of the surface electrode, the thickness of aportion other than the thin portion is preferably the same as thethickness of the central section of the surface electrode.

The width (the length represented by W1 in FIG. 7 ) of the peripheralsection of the surface electrode is not particularly limited and ispreferably 15 μm to 1 mm.

The width (the length represented by W3 in FIG. 7 ) of the thin portionis preferably 10 μm or more, more preferably 15 μm or more, and furthermore preferably 20 μm or more.

In the third embodiment of the present invention, the width of the thinportion refers to the distance from an end portion (preferably the inneredge of the covering ceramic layer) on the center side of the surfaceelectrode to a portion which is located on the peripheral side of thesurface electrode and which has the same thickness as the thickness ofthe central section.

In the third embodiment of the present invention, it is characteristicthat the width of the thin portion is 20% or more of the width of theperipheral section of the surface electrode that is covered by thecovering ceramic layer. That is, it is characteristic that the ratio(W3/W1) of the width W3 of the thin portion to the width W1 of theperipheral section of the surface electrode is 20% or more as shown inFIG. 7 .

The width of the thin portion is preferably 50% or more of the width ofthe peripheral section of the surface electrode that is covered by thecovering ceramic layer, more preferably 70% or more, further morepreferably 90% or more, and particularly preferably 100%. The case wherethe ratio of the width of the thin portion is 100% corresponds to thesecond embodiment of the present invention.

The central section of the surface electrode that is not covered by thecovering ceramic layer may have the thin portion. Only the peripheralsection of the surface electrode preferably has the thin portion.

The thickness of the thin portion is preferably 10 μm or less and morepreferably 5 μm or less.

As described above, in the third embodiment of the present invention, aposition where the thin portion is present and the width of the thinportion are different from those described in the second embodiment.Other constituents of the ceramic electronic component are the same asthose described in the second embodiment.

In the third embodiment of the present invention, in the peripheralsection of the surface electrode that is covered by the covering ceramiclayer, forming the thin portion, which is thinner than the centralsection of the surface electrode, on the central side of the surfaceelectrode and adjusting the width of the thin portion to 20% or more ofthe width of the peripheral section of the surface electrode probablyallows a liquid phase to be supplied to the covering ceramic layer fromthe base ceramic layer through the thin portion as is the case with thesecond embodiment. In particular, in the third embodiment, the liquidphase is probably likely to be supplied to an end portion of thecovering ceramic layer that is most likely to be peeled off as comparedto the second embodiment. As a result, the sinterability of the coveringceramic layer on the surface electrode is increased and the bondstrength between the covering ceramic layer and the surface electrode isincreased. Therefore, even in the case where the ceramic electroniccomponent is subjected to a surface treatment such as blasting, thecovering ceramic layer is unlikely to be peeled from the surfaceelectrode.

EXAMPLES

Examples disclosing a ceramic electronic component according to thepresent invention in detail are described below. The present inventionis not limited to the examples only.

[Confirmation of Effect Due to Openings]

The following components were prepared by the method described in thefirst embodiment: ceramic electronic components 1-1 to 1-4 eachincluding a surface electrode placed on a surface of a base ceramiclayer and a covering ceramic layer covering a peripheral section of thesurface electrode, the peripheral section of the surface electrode thatwas covered by the covering ceramic layer having openings.

FIG. 8 is a schematic plan view showing the shape of openings formed inthe peripheral section of the surface electrode in the ceramicelectronic component 1-1.

In the ceramic electronic component 1-1, the surface electrode 20 wasformed on the base ceramic layer 11 by screen printing using a screenmask having gaps, placed at intervals of 0.05 mm, having a width of 0.05mm such that a plurality of slits 41 with a size of 2 mm square wereprovided in the peripheral section, which was located 0.1 mm inside theperiphery.

FIG. 9 is a schematic plan view showing the shape of openings formed inthe peripheral section of the surface electrode in the ceramicelectronic component 1-2.

In the ceramic electronic component 1-2, the surface electrode 20 wasformed on the base ceramic layer 11 by screen printing using a screenmask having 0.02 mm square holes placed at intervals of 0.02 mm suchthat a plurality of holes 42 with a size of 2 mm square were provided inthe peripheral section, which was located 0.1 mm inside the periphery.

In the ceramic electronic component 1-3, after an electrode with a sizeof 2 mm square was formed, a laser was applied to the electrode so as topenetrate the electrode only, whereby the surface electrode was formedon the base ceramic layer so as to have holes, having a diameter of0.015 mm, placed at intervals of 0.015 mm in the peripheral section 0.1mm inside the periphery.

In the ceramic electronic component 1-4, the surface electrode wasformed on the base ceramic layer in such a manner that after anelectrode with a size of 2 mm square was formed on a PET film and holeswith a diameter of 0.01 mm were formed at intervals of 0.01 mm in aperipheral section located 0.1 mm inside the periphery of the electrode,using a puncher, the electrode provided with the holes was transferredto a base ceramic green sheet such that a plurality of holes wereprovided in the peripheral section.

A ceramic electronic component 1-5 including a surface electrodeincluding a peripheral section having no opening was prepared separatelyfrom the ceramic electronic components 1-1 to 1-4.

The ceramic electronic components 1-1 to 1-5 were blasted for thepurpose of removing surface stains. After blasting, ten pieces of eachceramic electronic component were cross-sectionally polished and whetherdelamination occurred at the interface between a covering ceramic layerand a surface electrode was checked, whereby the bond strength betweenthe covering ceramic layer and the surface electrode was evaluated.

For the bond strength between the covering ceramic layer and the surfaceelectrode, one in which no delamination occurred at the interfacebetween a covering ceramic layer and a surface electrode was rated A(excellent), one in which delamination occurred in one to less than ninepieces was rated B (good), and one in which delamination occurred in allten pieces was rated C (poor). The results are shown in Table 1.

TABLE 1 Bond strength between Method for forming covering ceramic layerNo. openings and surface electrode 1-1 Slits formed by printing A 1-2Holes formed by printing A 1-3 Holes formed with laser A 1-4 Holesformed with puncher A  1-5* No openings C

In Table 1, the ceramic electronic component 1-5, which is asterisked,is outside the scope of the present invention.

As is confirmed from Table 1, in the ceramic electronic component 1-5,in which the peripheral section of the surface electrode has noopenings, delamination occurred at the interface between the coveringceramic layer and the surface electrode, whereas in the ceramicelectronic components 1-1 to 1-4, in which the peripheral section of thesurface electrode has openings (slits or holes), no delaminationoccurred at the interface between the covering ceramic layer and thesurface electrode and the bond strength between the covering ceramiclayer and the surface electrode is high. In the ceramic electroniccomponents 1-1 to 1-4, the openings after firing were filled with aliquid phase supplied from the base ceramic layer.

From the about results, it is conceivable that forming openings in aperipheral section of a surface electrode allows a liquid phase to besupplied from a base ceramic layer to a covering ceramic layer throughthe openings, thereby increasing the bond strength between the coveringceramic layer and the surface electrode.

[Confirmation of Effect Due to Thin Portion]

The following components were prepared by the method described in thesecond embodiment: ceramic electronic components 2-1 to 2-4 eachincluding a surface electrode placed on a surface of a base ceramiclayer and a covering ceramic layer covering a peripheral section of thesurface electrode, the peripheral section of the surface electrode thatwas covered by the covering ceramic layer having a thin portion.

In the ceramic electronic components 2-1 to 2-4, the width of the thinportion was fixed to 100% of the width of the surface electrode and thethickness of the thin portion was varied over values shown in Table 2.

The ceramic electronic components 2-1 to 2-4 were evaluated for the bondstrength between the covering ceramic layer and the surface electrode bysubstantially the same method as the above. The results are shown inTable 2.

TABLE 2 Thickness of thin Bond strength between portion covering ceramiclayer and No. [μm] surface electrode 2-1 20 B 2-2 15 B 2-3 10 A 2-4 5 A

As is confirmed from Table 2, in the ceramic electronic components 2-1to 2-4, in which the peripheral section of the surface electrode has thethin portion, delamination can be prevented from occurring at theinterface between the covering ceramic layer and the surface electrode.In particular, in the ceramic electronic components 2-3 and 2-4, inwhich the thickness of the thin portion is 10 μm or less, nodelamination occurred at the interface between the covering ceramiclayer and the surface electrode and the bond strength between thecovering ceramic layer and the surface electrode is high.

From the about results, it is conceivable that forming a thin portion ina peripheral section of a surface electrode allows a liquid phase to besupplied from a base ceramic layer to a covering ceramic layer throughthe thin portion, thereby increasing the bond strength between thecovering ceramic layer and the surface electrode.

REFERENCE SIGNS LIST

-   -   1, 2, 3, 4, 5 Ceramic electronic component    -   10 Electronic component body    -   11 Base ceramic layers    -   20 Surface electrode    -   21 First sintered layer    -   22 Second sintered layer    -   23 Plating layer    -   30 Covering ceramic layer    -   40 Openings    -   41 Slits    -   42 Holes    -   50 Thin portion    -   W1 Width of peripheral section of surface electrode    -   W2, W3 Width of thin portion

The invention claimed is:
 1. A ceramic electronic component comprising:an electronic component body including a superficial base ceramic layer;a surface electrode on a surface of the electronic component body,wherein the surface electrode includes a first sintered layer on thesuperficial base ceramic layer, and a second sintered layer on the firstsintered layer; and a covering ceramic layer covering a respectiveperipheral section of the first sintered layer and the second sinteredlayer of the surface electrode, wherein each of the respectiveperipheral section of the first sintered layer and the second sinteredlayer of the surface electrode that is covered by the covering ceramiclayer has a thin portion, wherein the thin portion of each of the firstsintered layer and the second sintered layer is thinner than arespective central section of the first sintered layer and the secondsintered layer of the surface electrode, and wherein a width of the thinportion is 20% to 90% of a width of the respective peripheral section ofthe first sintered layer and the second sintered layer of the surfaceelectrode that is covered by the covering ceramic layer.
 2. The ceramicelectronic component according to claim 1, wherein the width of the thinportion of each of the first sintered layer and the second sinteredlayer is 15 μm or more.
 3. The ceramic electronic component according toclaim 1, wherein a total combined thickness of the thin portion of eachof the first sintered layer and the second sintered layer is 10 μm orless.
 4. The ceramic electronic component according to claim 1, whereinthe first sintered layer contains a metal oxide containing at least onemetal element selected from Al, Zr, Ti, Si, and Mg.
 5. The ceramicelectronic component according to claim 4, wherein the second sinteredlayer contains the metal oxide in an amount smaller than that containedin the first sintered layer.
 6. The ceramic electronic componentaccording to claim 4, wherein the plating layer is not covered by thecovering ceramic layer.